In a scientific breakthrough, Ian Molineux, professor of molecular genetics and microbiology, observed viruses crawl across the surface of bacteria, scouting the membrane to infect the cell at its weak spot.
The observations, published this week in Science Express, provide new information that could fill current gaps in viral research.
“For 10 years, I have been drawing straight lines — in cartoon fashion — of how proteins go from the head through the [cell] wall,” Molineux said. “Now we can see it, and seeing is believing.”
Molineux said two details of the publication are surprising. Contrary to previous hypotheses, the bacteriophage — a specific type of virus that infects bacteria in order to replicate itself — contains five or six leg-like fibers that extend from the viral head. These fibers unfurl upon approaching bacteria, allowing the virus to scout the surface like a lunar lander. Additionally, the paper presents new evidence to suggest that the virus uses the inner membrane of the host cell for the initial energy needed to deploy proteins and DNA inside the cell.
Using cryo-electron tomography, the researchers observed the mechanics by which T7 bacteriophages unfold fibers and infect genetically modified E. coli bacteria that are about a quarter of their regular size. Molineux co-authored the article with Bo Hu, William Margolin and Jun Liu, from the UT Health Science Center at Houston.
“It’s an amazing thing, when you see something you only hoped for, and there it is.” Liu said,
Liu and Molineux met at a conference in Galveston where the two talked about the details of a previous article that Liu had published with Margolin about a P1 bacteriophage.
“We were building on a lot of assumptions, hoping that the same model would apply to my research with the T7,” Molineux said. “We try to work on [these] assumptions, a house of cards you could say. Well, now this house has mortar and bricks.”
According to the published article, some aspects of the findings may be limited to the T7 bacteriophage.
“We don’t know how common it is for the bacteriophage to walk on the cell since they hadn’t been seen doing it until now,” Margolin said. “Normally they are very difficult to see: when you use a light microscope, the image is not clear, and when you use a transmission electron microscope, it is clear but full with chemicals. The cryo-electron tomography ends up being the middle point we were looking for.”
The team’s animation, uploaded to YouTube earlier in the week, depicts the T7 walking.
Published on January 16, 2013 as "UT professor's findings advance virus research".